Solid ink or phase change ink printers conventionally receive ink in a solid form, either as pellets or as ink sticks. The solid ink pellets or ink sticks are typically inserted through an insertion opening of an ink loader for the printer, and the ink sticks are pushed or slid along the feed channel by a feed mechanism and/or gravity toward a heater plate in the heater assembly. The heater plate melts the solid ink impinging on the plate into a liquid that is delivered to a print head for jetting onto a recording medium.
One difficulty faced in solid ink technology is differentiation and identification of ink sticks to ensure the correct loading and compatibility of an ink stick with the imaging device in which it is used. Provisions have been made to ensure that an ink stick is correctly loaded into the intended feed channel and to ensure that the ink stick is compatible with that printer. One such provision is directed toward physically excluding wrong colored or incompatible ink sticks from being inserted into the feed channels of the printer. For example, the correct loading of ink sticks has been accomplished by incorporating keying, alignment and orientation features into the exterior surface of an ink stick. These features are protuberances or indentations that are located in different positions on an ink stick. Corresponding keys or guide elements in the ink loader of the phase change ink printer exclude ink sticks which do not have the appropriate perimeter key elements while ensuring that the ink stick is properly aligned and oriented in the feed channel. Due to the relatively small size of ink sticks, visually recognizable words, numbers or other such identifiers, are correspondingly much smaller so it is generally impractical to apply identifiers more extensive than a logo or color slot symbol on surfaces of the sticks that would be viewed by a user. Manufacturing limitations and ink material robustness vulnerability, such as scrapes, cracking, flaking, chipping and the like, have historically prevented application of such identification on ink sticks.
World markets with various pricing and color table preferences, however, have created a situation where multiple ink types may exist in the market simultaneously with nearly identical size/shape ink and/or ink packaging. Thus, ink sticks may appear to be substantially the same but, in fact, may be intended for different phase change printing systems due to factors such as, for example, ink formulation, service/supplies contracts, market pricing or color table. Due to the broad range of possible ink stick configurations, marketing strategies, pricing, etc., differentiating the inks sticks so only appropriate ink is accepted by a printer requires various ink shapes and physical keying. The resulting proliferation of various different ink stick configurations representing different part numbers or stock keeping unit numbers creates problems of identification since historical stick forms, absent packaging, cannot be easily or accurately deciphered as to intended usage. This situation can arise at locations where multiple product models are in use simultaneously or with bulk storage of unpackaged ink, such as at a manufacturing facility, distribution center or customer site. Unpackaged bulk ink may be an aspect of a waste reduction effort by a supplier or customer. These and similar situations are becoming increasingly significant because of different ink formulations and concurrent sales arrangements or programs in a global market place. Ink sticks with feature sets that can be conveniently translated into useful identification are needed.